First thing...certo is used for making jelly...can be found in most grocery stores in the canning section...as for mixing..I use a 32oz bottle of gatorade mix one packet of the certo with it...as for sub..can't be done you drink the certo and gatorade a couple hours before the test...normally good for about 4 hours...this method won't work if its a random test that you don't have at least a couple hours to prepare for...