Yes, the phrase "SUGGESTIONS TO SIWES COORDINATORS" is grammatically correct.
**Meaning:** It implies that the following text or content will provide recommendations or advice directed towards coordinators involved in the Student Industrial Work Experience Scheme (SIWES).
**Rephrasing Options:**
1. Recommendations for SIWES Coordinators
2. Proposals for Coordinators of the SIWES Program
3. Advice for SIWES Program Coordinators
4. Suggestions