For user acquisition hacks for SAAS prototypes, focus by leveraging targeted digital marketing strategies such as content marketing, SEO, and social media advertising to generate initial interest and drive traffic to your prototype. Utilize referral programs, beta testing, and partnerships with industry influencers to attract early adopters and generate buzz around your product. Additionally, offer exclusive access or limited-time discounts to incentivize sign-ups and gather valuable feedback for further refinement of your SAAS prototype.