As others have said with this sort of timescale the most important thing is to preserve principle and you can't afford to risk losing that 1m (I'm assuming)
If you really feel the need to take some risk, what you could do is gamble the interest. Put 999,500 into a savings account at 1% for three weeks, after which it will be worth 999,500 x 1+(0.01x3/52) 1,000,076. Obviously if the time or interest rate is different from this you need to recalculate the amount you can risk - and check the math yourself.
This gives you 500 that you can put at risk and still be able to repay that 1mm. Of course 500 sounds much less impressive, but remember you can take a pretty high risk with it as your principle is already secured. For shares I'd use it to buy options in order to get the most potential return. Or buy lottery tickets, gamble on sport, hell put it all on red. Just whatever you do don't leverage eg cfd's, spread bets of anything where you can lose more than your 500, otherwise you're still risking your million (or your own savings) to cover the margin. Point of the exercise is that worst case you should never end up with less than 1mm. Assuming the savings bank doesn't crash but hey that's a different question.
Whenever you see a bank advertising a guaranteed equity bond eg "we'll guarantee to return your money after 5 years, plus 5% of any increase in the s&p500 provided that the moon is rising in Aquarius (or some other bs condition)" this is what they are doing.