Nah, you'll be fine as long as you aren't over-sensitive to caffeine or on heart medication or something:

• Baja Blast has about 54 mg of caffeine per 12 ounce can, putting it at 225 mg of caffeine if you filled the entire tumbler with it.
• Dew Zero is 69 mg per 12 ounces, which would be about 287.5 mg for this thing.

As for regular coffee/energy drink serving sizes:

• A single 16 ounce Monster Java is around 200 mg, and an Absolute Zero is in the neighborhood of 140 mg.
• A cup of strong coffee is between 250 and 350, and Death Wish claims to be 666 mg.