2 small to medium watermelons
1 to 2 cups margarita mix
Wash and dry watermelons. With a long, sharp knife, mark off a 5 to 6-inch circle on top of the watermelons. Cut a deep cone into the center of each watermelon. Remove the plug. Turn watermelons over and let them drain for about 30 minutes; discard juice.
Turn melons open side up. Into one pour 1/2 to 1 cup liquid margarita mix.
To fill cavity, wait a bit and add more as it is absorbed (if using dry Margarita mix, prepare as directed and fill melons).
For second melon, measure a similar amount of mix and combine with tequila, using 3 parts mix to 1 part tequila. Pour into second watermelon.
Let melons stand as liquid is absorbed. Replace plug. Mark one melon alcoholic and the other melon non-alcoholic.