Long story short I need to get 15 credits. No CLEP allowed unfortunately.
There’s not really a “fastest” way to do it. To get 15 units, you need to take 15 units. I suppose you could always take the max your college/university allows during summer and technically that will be faster than taking them during a full semester, but then again taking 15 units over summer is almost impossible unless you’re doing absolutely nothing else during the summer and you have amazing time management skills.
You can take distance learning courses at many universities and complete them at your own pace.