So now you've made your beaters let's find something to hit. At this point I should really mention health and safety. Although my own view is that health and safety policies are a curse and a kill-joy, nevertheless I realise that saying so in court will do little to reduce my penalty. I once asked a class of 12yr olds to 'bring in a home made instrument next week'. When next week came I was met with tin cans with jagged edges and glass bottles played with heavy sticks. In the event there were no breakages or injuries but I should have seen it coming. So if you are working with young children you may which to take reasonable precautions against injury.
In Europe the ubiquitous 2ltr (about 70 fluid ounces) plastic bottle makes an excellent first drum. When empty and without the cap it makes a satisfyingly resonant sound when struck with your home made beater. Compare the sound of the base with the side and do you prefer to used the rubber head of the beater or the wooden end? How about using the side of the stick? And when you hit the bottle hard does the sound just get louder or change in other ways? Experiment with the bottle and find the best places to hit. You could mark the 'sweet spots' with a permanent marker pen.
The great thing about plastic bottles is that they can be held fairly firmly without damping. Some materials, metal in particular, can have their natural resonance restricted by holding. However, too strong a grip will have an impact on your botle so again, experiment and find the optimum firmness.
If you hit the bottle hard enough, often enough, the plastic will lose its 'memory' or suffer punctures. Your students will have fulfilled the urge to test the instrument to destruction and it can now be recycled in the usual way. Replacement will not impact on your pocket or departmental budget.
Smaller plastic bottles tend to be too thin. A half litre bottle, hit on the side, requires subtlety and will not give much volume. The base, however, is surprisingly strong and gives a higher note than a larger bottle. Bigger plastic bottles, like the 5ltr (gallon) one in the picture are usually more robust although I prefer round sided bottles to this flat sided example.
Here is a recording I made this afternoon of the 5ltr bottle (lid left on), 2ltr and 500ml bottles (lids removed). Ignore the loose drumming and enjoy the sounds of the bottles played together. Just to be clear, I didn't play them all at once but overdubbed them using a trial version of Ableton Live. And I used my home made beater throughout.