"Properly" is the key word here, because the devil is in the details. If you were to go directly to a dentist with this question, they would undoubtedly tell you that there is no real alternative to spending the appointed time with good old toothpaste and tooth brush, not to mention a thorough flossing to boot!
I'll be the first to admit that I have previously been known to do a quick once-over with a toothbrush without any toothpaste, but it turns out that this practice is likely to cause micro-scratches in the enamel of one's teeth--just the thing, as long as you want to help stains and food particles to stick to your teeth in the long run.
I'll also speak for the crowd and say that flossing is the natural first sacrifice that folks tend to make when they're in a hurry, and this is a fairly okay option from time to time, as long as you don't make a habit of it. If you're the sort of person who would otherwise forget about flossing altogether, then it would even be advisable to go as far as setting yourself an alarm to force it into your schedule every now and then.
As far as time efficiency goes, mouthwash is your best friend; the time used for swishing is ideal for multitasking, as the rest of your body is completely free in the meantime. Whatever else you need to get done in that same time frame-- get dressed, use the bathroom, take a shower, throw a bagel in the toaster-- time spent rinsing with mouthwash need not count against your busy schedule, and so I would alwaysalways make sure to do this.
On the subject of plain old brushing (with toothpaste, or a water pik, or one of those disposable on-the-go brushes, or whatever), there is an obvious time tradeoff available: how long is long enough? The answer is pretty much up to you. You should never skip this step altogether if you can possibly help it, but the exact duration is less important than the fact of brushing (all surfaces, not just the easy-to-reach ones) in the first place. If you also use mouthwash, for example, then it may be justifiable to reduce your brush time when you're in a hurry-- as long as you still make sure to spend the time to do a thorough job whenever you aren't in a hurry (especially after you eatif you've recently eaten sugary and/or acidic foods like fruit, sweets, soda, and juice).
The big takeaway:
Dental health, much like dietary habits and many other things, is all about moderation. As long as you still keep up good habits in the long run, you can get away with minor discrepancies every now and then; and vice versa, if you're going to take shortcuts every now and then, that makes it all the more important that you keep up good habits in the long run.
P.S. While I'm at it, here's a bonus protip for you:
Follow your consumption of sugary, acidic, or staining food and drink (sweets, fruit, soda, juice, coffee, tea, you name it) with a glass of uncarbonated water or milk, or by chewing a piece of sugarfree gum! Each of these will help to neutralize, dilute, and rinse away the offending substances, and thereby reduce the likelihoodamount of your teeth being harmederosion and/stainedor staining that can occur.